Known methods for dispensing sealing compositions formed by mixing together predetermined quantities of two components that, after being mixed with each other, will react with each other to form a resiliently flexible solid sealing composition include the use of multiple syringe-type dispensers that meter individual components at point of use into either a static or mechanically agitated mixer. Such dispensers have many disadvantages which can include difficulty in dispensing due to high back pressure, being cumbersome, having overall length and geometry that is poorly suited to the application, providing inefficient mixing, and presenting significant limitations on the volume ratios of components that may be mixed.
A known dispensing assembly used for dispensing a single component sealing material that is commercially available as the "Avon" model applicator gun from P. C. Cox, Newbury, England, comprises an elongate barrel having a through opening with a generally uniform cross sectional area, a plunger adapted to move along the through opening between rear and front ends of the barrel, manually activatable driving means for forcefully driving the plunger from the rear end to the front end of the barrel, a nozzle having a through passageway converging from an inlet to an outlet end and having a cross sectional area at its inlet end that is about the same as the cross sectional area of the through opening, and means for removably mounting the inlet end of the nozzle on the front end of the barrel. Typically, the single component sealing material to be dispensed by this assembly is packaged in a "sachet" comprising a generally cylindrical tube of flexible film, optionally with moisture and/or solvent barrier properties, which tube has heat seals, metal clips, or other closures at its ends. That sachet package is inserted into the through opening in the barrel, a portion of the periphery of the flexible package adjacent the front end of the barrel is removed, the inlet end of the nozzle is attached to the front end of the barrel, and the driving means is activated to compress the flexible sachet package and thereby dispense the sealing material through the nozzle. No separate seal is required between the sachet package and the nozzle. After all of the sealing material has been dispensed, the crushed sachet package and the nozzle are removed and discarded. Little, if any, of the sealing material will have been deposited on the inner surface of the barrel so that clean up of the barrel is minimal.
Flexible packages are known that comprise two opposite flexible walls having peripheries firmly attached to each other (e.g., by heat sealing or otherwise) to form a main chamber between the walls with the walls being separably attached to each (e.g., by a rupturable heat seal) along a line extending between spaced parts of those peripheries to divide the main chamber into two temporary main chamber portions, each sized to contain a different one of two parts or components. Examples of such a package are described in U.S. Pat. Nos. 2,932,385, 3,074,544 and 3,087,606. The components in such a package can be mixed by manually rupturing the seal along the line and kneading the package by hand to mix the components. As is described in U.S. Pat. No. 4,168,363, the components used in such a package can be fluid , but when mixed can thicken rapidly to a grease-like, non-flowing consistency for ease of application.
It is known to formulate polyurea-urethane compositions (e.g., sealants, coatings, foams, and the like) as two component systems. One component includes the isocyanate-reactive components such as polyols, together, typically with a catalyst and other customary additives, while the second component includes the polyisocyanate. The catalyst is separately packaged from the polyisocyanate in order to prevent premature gelation of the latter material. The two components are normally mixed immediately prior to application of the coating. Upon mixing the two components, the hydroxyl groups of the polyol chemically react with the isocyanate groups of the polyisocyanate, ultimately leading to gelation. At gelation, the reaction mixture rapidly loses its fluidity with an attendant pronounced increase in viscosity.